Vinyl is the least expensive option. Inside a suitable excavation, a frame of wood, plastic or metal is erected. The most stable systems are set in a concrete footing. Wall panels are then fastened to the framing, plumbing is installed, and a sand base is laid. A heavy-duty vinyl liner is fastened to the top of the frame and what remains of the hole is backfilled. Masonry coping is installed over the top of the wall.
Fiberglass pools are pre-molded in a variety of shapes and sizes. They are manufactured with steps, benches, and swimouts already in place (not the case with vinyl). After the hole has been dug, plumbing installed, and sand base laid, it is lowered into the hole and leveled. To avoid bowing, filling the pool with water and backfilling with sand must be done simultaneously. No framing is required.
Shotcrete pools are made by shooting a mix of cement, sand, water, and aggregate from a pneumatic applicator at high speeds against the earthen walls and base of the pool excavation and around a grid woven of steel rebar (reinforcing bar). Multiple passes are necessary to build the mixture to the desired thickness. The concrete must be troweled smooth before it sets, and afterwards a coat of plaster is applied.
There are two types of shotcrete, wet and dry. Wet shotcrete is delivered premixed with water in a truck. Dry shotcrete, commonly known as Gunite, is a mix of sand and cement and sometimes small aggregate. It remains dry until it reaches the nozzle of the applicator and doesn't really mix with water until impact on the pool walls and floor. There is some debate about which approach is stronger and longer lasting, but both processes produce durable pools. Gunite, however, demands a more highly skilled nozzle man to maintain the correct water-to-cement ratio.